1. Field of the Invention
The present invention is related to a wireless communication system, and more particularly, to a wireless communication system using a single trace for transmitting signals, conducting DC signals and cutting off DC signals.
2. Description of the Prior Art
With the rapid development of technology, various electronic devices, such as blue-tooth devices, global positioning systems (GPSs), satellite radios or multi-media equipment, can be integrated together, providing drivers and passengers with vehicles not only capable of transportation, but also serving as mobile digital centers. In order to provide the drivers and passengers with wireless communication, a receiving module, such as a satellite radio, is disposed inside a car. An antenna is disposed outside the car for receiving signals.
Please refer to FIG. 1 for a diagram illustrating a prior art wireless communication system 10 used in a car. The wireless communication system 10 includes an active antenna 12, a receiving module 14, a power source 16, and two in-car traces. The in-car traces of the wireless communication system 10 include a power line 17 and a high-frequency signal line 18. The receiving module 14 is coupled to the power source 16 and the active antenna 12 via the power line 17 and the high-frequency signal line 18, respectively. Therefore, the receiving module 14 can receive direct current (DC) signals generated by the power source 16 via the power line 17 and high-frequency signals sent by the active antenna 12 via the high-frequency signal line 18. Also, the DC signals generated by the power source 16 are transmitted to the active antenna 12 via the power line 17 and the high-frequency signal line 18 sequentially. The receiving module 14 controls passages of the DC signals. The prior art wireless communication system 10 requires two in-car traces for signal transmission. Therefore, the trace layout is complicated and causes inconveniences for users.
Please refer to FIG. 2 for a diagram illustrating another prior art wireless communication system 20 used in a car. The wireless communication system 20 includes an active antenna 22, a receiving module 24, a power source 26, and an in-car trace. The in-car trace of the wireless communication system 20 includes a high-frequency signal line 28. The receiving module 24 is coupled to the power source 26 and the active antenna 22 via the high frequency signal line 28, and can thus receive DC signals generated by the power source 26 and high-frequency signals sent by the active antenna 22. Also, the DC signals generated by the power source 26 are directly transmitted to the active antenna 22 via the high-frequency signal line 28. The prior art wireless communication system 20 has a simpler layout by using only one in-car trace for signal transmission. However, the users cannot control power sent to the active antenna 22 using the receiving module 24. Therefore, the prior art wireless communication system 20 consumes more power.